Overload switch



July 28, 1925.

L. SCHON ET AL OVERLOAD SWITCH Filed Sept. 4, 1920 15 France,

the

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' this Patented July 28, 1925. i

UNITED. STATES PA ENT- OFFICE.

mnwrc senor Am) uxoa rraarzscmn, or nssmz, em, assrenoas 'ro ramp. xaurr mmneasamscuarr, or assumes-masons, smear.

OVERLOAD SWITCH.

Application fled September-4, 1920. Serial ll'o. 408.388.

clump mm. m raovlsrons or rm: ACT or nner! 3, 1921, 41 area. n, 131:.

To all whom it may concern.-

Be it lmown that we, LUDWIG ScHiiN, residing at Essen, German and JAKOB Prnnrzsonnnn, residing at ssen, Germany,

both citizens of the German Republic, have 21, 1917 Austria No. 88,510, filed September 26, 1918; Switzerland, No. 87,295, filed 4 April 30, 1920; Holland, No. 7,135, filed May 14,1920; Sweden, No. 49,664, filed June 19, 1920; S ain, No. 74,424, filed July 3, 1920; 0. 523,357, filed July 7, 1920.; and Italy, No. 25/548, filed Jul 3, 1920), of which the following is a specification.

This invention relates to overload switches havin a power storing device and a magnetic field adaptedito be excited both by the current of the circuit which is to be protected and by an auxiliary current. The ob-' ject of the invention is to provide an overload switch of the above referred to which shall be suita le for every kind of current A. C'. orD. O. and which possesses roperty of not being able to switch itself in again after the removal of the dis turbing cause but on the contrary remains open until the auxiliargxscircuit is opened by hand. The deviceis tinguished by simplicity of co" ruction convenience of manlpulation an great reliability of action.

The invention will 'be described with reference to theaccompanymg in which-(1i 'cally 1 and 2 show a circuit arran I ment' j for protecting a. direct current supp y cir cult. I r

3 shows a-similar arrangement applied'to a Leonardmotor generator set.

,In the first form shown in Figure 1 it is assumed that a translating device (not w 7 shown), such as a continuous current motor for. example, though theembodiment is not limited to direct current, is to be rotected from overload 'bfy the overload switch. In A' denotes the main current winding, A the magnet ,core and A the 0 contact brush of a direct acting electro-magnetic switch rigidly connected to the core of 'the magnet; is a tension spring, which tends put the contact brush A 'mto concore A are .so proportion 1 current strength arises in rangement let it be assumed current winding A and with the interruption points A, A in series therewith, an

auxiliary winding A. In the main current circuit is also rovided a two pole hand 0perated switch' which serves to cut off the current from the current consumer and from the auxiliary winding A atthe same time.

The automatic switch parts A, A to A (not shown) closed consisting of "the is enclosed in a casing on all sides.

. The two magnet windings A and A which act in the same direction u on the magnet and arranged 'that their common pull in the direction in WhlCh the switch is opened is les than the oppositely directed pull of the spring A,

so long as the main current winding is traversed y the normal or a smaller current, but that their pull overcomes the power of the spring as soon as a nonlpermis'sible high e main' current circuit, that is to sa in the circuit of the current consumer. A is 'so pro rtioned that its pull alone will suflice un er complete excitation to hold the switch open with'the contact brush A awa from the contact blocks "A and A,

m e position shown in Figure 1, but it cannot 'open the switch when in the closed position without the co-operation jof the main current winding A traversed by a nonpermissible high current, because when the switch is closed the auxilia winding A i practically short-circuited h'y way of A,

In considering the workin of the arfiiat'both the automatic switch A, A, A, as well as the hand operated'switch B are in closed position, so that the translating device receives current from thesource. If now, for example, say by overloading of the motor, an-

overload arises the circuit of the translating device, the switch A, A, A, opens e auxiliary winding under the action of the main-current wrn'dingAP' As the counter electromotive force of the 'motor orthelike disappears rapidly as soon as the circuit the current Ill winding A is interrupted, the auxiliary winding A, after the switch A A A is opened receives the full potential from the source of current, so that it will be. fully excited and is able to hold the switch fast in the open position. i 1- Afterthe removal oif'the disturbing cause the switch B is-first opened by hand, wherea by the currentis out ofl from the winding A and the switch A A, A, again closes through a switch C,- which is conveniently constructed as a push switch, to the two sides of the main, supplied by the contlnuous current generator'and that the hand operated switch B is therefor dispensed with. If the switch A A, A, and likewise the switch C are in closed position, both magnet windings Aand A are excited.

If now the current strength in the main current circuit rises for any reason to an excessive degree (e. g. owing to a short circuit on the main), the switch A A", Af, is

opened as shown under the' action of the tractive force of both, wmdings A and A,

- which overcomes the power of the spring.

In-order to again close the switch A A", A, after the removal of the dlsturbing cause, it is only necessary to temporarily interrupt the current in the auxiliary winding A by opening the switch C. This cuts the current ofi from the auxiliary winding A and the switch moves into its closed position. If contrary to expectation a nonpermissible high current still prevails, the switch A", A, A, immediately opens again,

- whereas it remains closed-if the current in I same magnetic circuit t ploy the sameyoke.

the meantime has dropped to the permissible value. It may-be stated that when dealing with alternating current circuit'coils A and A are not necessarily a' ranged to havethe ough they may em- Figure 31 hows a form of the switch suitable f orworking with a Leonard motor generator set. o y

In this case the .maln current winding as included in the common armature circuit of the Leonard generator D and the motor E belonging thereto. Theswitch A, A, A,

on the other hand is included in the exciting circuit of the generator D. The auxiliary winding A is connected through a switch F to the source of current of constant tension which supplies the exciting current.

The working of the apparatus is similar to that of the arrangement shown in Figure 2. The diiierence is that the current is cut off from the armature circuit without it being necessary to interrupt the circuit.

If the automatic switch is to protect the Leonard motor generator set against current impulses also, in which the direction of the current in the armature-circuit is reversed, as happens when the motor E is braked electrically, it is convenient to construct the switch with separate magnetic circuits for themain current and for the auxiliary winding," As the auxiliary winding A is so proportioned that its magnetic tractive force is suflicient in all cases, to hold the switch ino en position, variations in the strength 0 the magnetic field of the main current winding A are not able,

when separate magneticj circuits are employed, to bring the switch into closed position. Thisprevents any premature clos ing owing to the reversal of the current in the main current winding.

Claims: I

1. A11 overload switch device for protecting an electric circuit, comprising means tending to close the switch, a main circuit whose-current is controlled by the operation of the switch, an' auxiliary circuit whose current is permitted to flow independent of said switch control, means dependent upon the simultaneous flow of-excessive main and of the auxiliary current,

for opening said switch against said closing means, but adapted to retain the switch in open position by the auxiliary current alone then flowing, the relation of the force of said switch closing means to the magnetic tractive force exerted by the current traversing mined that the switch remains in its open position until said auxiliary circuit is broken.

2. An overload switch device for protecting an electric circuit, comprising means tending to close the switch, a main circuit whose current is controlled by the operation of the switch, an auxiliary circuit whose current permitted to flow independent of said switch control, means dependent upon thesimultaneous flow of excessive main and of the auxiliary current, for opening said switch against said closing means, but adapted to retain the switch in open position by the auxiliary current alone then flowing,'the relation of the force of said switch closing means to the magnetic tractive force exerted by the current traverssaid auxiliary circuit being so detersaid auxiliary circuit being so determined that the switch remains in 'its' o n position said" auxiliary crcuit is bro en and means for cutting 01! at will the auxiliary current supply to permit the closing of said switch.

3. An overload switch device for protecting an electric circuit, comprising means tending t close the switch, a main circuit whose current is controlled by the operation of the switch, an auxiliary circuit whose current is permitted to flow independent of said switch control, means dependent upon the simultaneous fiow of excessive main and of the auxiliary current.v tor opening said switch against said closing means, but adapted to retain the switch in open position by the auxiliary current alone then flowing, the relation of the force of said switclrclosing means to the magnetic tractive force exerted by the current traversing said auxiliary circuit being so determined that the switch remains in its open position until said auxiliary circuit is broken, and

means for cutting off at will the auxiliary current supply 'to permit the closing of said switch, said cutting-off means being inserted in said main circuit.

4. In combination, a main circuit, an eleo-- ,ing through both of said elements whereby said main element is disconnected, said auxiliary element being adapted to maintain said switch in open position against the action of said mechanical means, and means for cutting off at will the current supply to said auxiliary element.

5. In combination with an electric switch,

.a mechanical means normally tending to close said switch, electromagnetic means comprising a main and auxiliary element for opening sald switch against the action of said mechanical means on a predeter- The foregoing specification signed at Essen, Germany, this 18th day of May, 1920.

HANS Go'rrsMANN,

J OSEF OLBERTZ. 

